Pump with bleed mechanism for reducing cavitation

Abstract

A gear pump assembly includes a drive gear having a plurality of circumferentially spaced teeth, and a driven gear likewise having a plurality of circumferentially spaced teeth positioned for intermeshing engagement between the drive and driven gears via the teeth. A bleed mechanism directs carryover fluid from a discharge side of a bearing dam to an inlet side of the bearing dam in order to supply the carryover fluid to a carryover volume disposed between mating drive gear teeth and driven gear teeth. The bleed mechanism including a passage communicating with at least one of (i) a gear face of the drive gear, (ii) a gear face of the driven gear; or (iii) a bottom of a gear tooth profile adjacent a root region between adjacent gear teeth.

We claim: 
     
       1. A gear pump assembly comprising:
 a drive gear having a plurality of circumferentially spaced teeth; 
 a driven gear having a plurality of circumferentially spaced teeth that mesh with the teeth of the drive gear whereby rotation of the drive gear results in rotation of the driven gear; 
 a bearing dam that directs a carryover volume from a discharge side of the pump assembly to an inlet side of the pump assembly; 
 a bleed mechanism that supplies bleed fluid flow to the carryover volume disposed between mating drive gear teeth and driven gear teeth, the bleed mechanism including a passage in at least one of the drive gear and driven gear teeth, the passage includes at least one first passage portion extending through the teeth of the drive gear and/or driven gear, the first passage portion having an opening in an axial end of at least one of the drive gear and the driven gear, and the first passage portion extends in a direction substantially parallel to opposite faces of the teeth of the drive and/or driven gear, the passage further communicating with at least one of: 
 (i) a non-working gear face of the drive gear, 
 (ii) a non-working gear face of the driven gear; or 
 (iii) a bottom of a gear tooth profile adjacent a root region between adjacent gear teeth; 
 the bleed mechanism further including a counter bore portion at the axial opening, the counter bore portion timing the bleed fluid flow to the bleed mechanism passage; 
 the bleed mechanism passage receiving the bleed fluid flow at the counter bore before directing the bleed fluid flow toward the gear mesh. 
 
     
     
       2. The gear pump assembly of  claim 1  wherein the passage includes a second passage portion communicating at a first end with the first passage portion within the drive and/or driven gear teeth, and communicating at a second end with a face of the teeth of the drive and/or driven gear, respectively. 
     
     
       3. The gear pump assembly of  claim 2  wherein the second passage portion is inclined relative to normal to one of the faces of the teeth of the drive and/or driven gear. 
     
     
       4. The gear pump assembly of  claim 2  wherein the second passage portion communicates with a non-working, trailing face of the gear teeth. 
     
     
       5. The gear pump assembly of  claim 2  wherein the second passage portion includes first and second openings that are inclined relative to normal to one of the faces of the teeth of the drive and/or driven gear. 
     
     
       6. The gear pump assembly of  claim 5  wherein the first and second openings of the second passage portion converge toward one another. 
     
     
       7. The gear pump assembly of  claim 1  wherein the counter bore portion is enlarged, the counter bore portion disposed at an inlet end of the first passage portion that communicates with the inlet side of the gear pump. 
     
     
       8. The gear pump assembly of  claim 1  wherein the bleed mechanism passage includes an axial slot that communicates with a side of the teeth at one end and that communicates with the root region disposed between adjacent gear teeth at the bottom of the gear tooth profile. 
     
     
       9. The gear pump assembly of  claim 8  wherein the bleed mechanism passage is in the drive gear, the bleed mechanism passage of the drive gear receives the bleed fluid flow from the inlet side of the pump via the axial opening before directing the bleed fluid flow toward a center of the gear mesh. 
     
     
       10. The gear pump assembly of  claim 8  wherein the bleed mechanism passage includes a connecting portion at the bottom of the gear tooth profile. 
     
     
       11. The gear pump assembly of  claim 10  wherein the connecting portion is angled to direct the bleed flow toward a face of the bearing dam. 
     
     
       12. The gear pump assembly of  claim 1  wherein the passage includes a second passage portion communicating at a first end with the first passage portion within the drive and/or driven gear teeth and the second passage portion communicates with a trailing face of the gear teeth; and 
       wherein the passage extends from the axial opening in the teeth of the drive gear to the trailing face of the drive gear teeth, or wherein the passage extends from the axial opening in the teeth of the driven gear to the trailing face of the driven gear teeth. 
     
     
       13. The gear pump assembly of  claim 10  wherein the connecting portion extends from the axial slot in the teeth of the driven gear to a leading face of the driven gear teeth. 
     
     
       14. The gear pump assembly of  claim 10  wherein the connecting portion extends from the axial slot in the teeth of the drive gear to a leading face of the drive gear teeth. 
     
     
       15. The gear pump assembly of  claim 1  wherein the passage includes a second passage portion communicating at a first end with the first passage portion within the drive and/or driven gear teeth;
 wherein the second passage portion communicates with a trailing face of the gear teeth; and 
 wherein the connecting portion extends from an axial slot in the teeth of the drive gear to the trailing face of the drive gear teeth. 
 
     
     
       16. The gear pump assembly of  claim 15  wherein the connecting portion extends from the axial opening in the teeth of the driven gear to the trailing face of the driven gear teeth. 
     
     
       17. The gear pump assembly of  claim 10  further comprising timing slots in bearing end faces to control flow into the axial opening. 
     
     
       18. The gear pump assembly of  claim 17  wherein the timing slots in the bearing end faces are provided in both an inlet side and discharge side of the bearing dam that separates the inlet side and discharge side of the pump assembly. 
     
     
       19. A gear pump assembly comprising:
 a drive gear having a plurality of circumferentially spaced teeth; 
 a driven gear having a plurality of circumferentially spaced teeth that mesh with the teeth of the drive gear whereby rotation of the drive gear results in rotation of the driven gear; 
 a bearing dam that directs a carryover volume from a discharge side of the pump assembly to an inlet side of the pump assembly; 
 a bleed mechanism that supplies bleed fluid flow to the carryover volume disposed between mating drive gear teeth and driven gear teeth, the bleed mechanism including:
 a passage in at least one of the drive gear and driven gear teeth, the passage includes at least one first passage portion extending through the teeth of the drive gear and/or driven gear, the first passage portion having an opening in an axial end of at least one of the drive gear and the driven gear, and the first passage portion extends in a direction substantially parallel to opposite faces of the teeth of the drive and/or driven gear, the passage further communicating with a side face of at least one of the drive gear and driven gear; and 
 a counter bore portion at the axial opening, the counter bore portion timing the bleed fluid flow to the bleed mechanism passage. 
 
 
     
     
       20. A gear pump assembly comprising:
 a drive gear having a plurality of circumferentially spaced teeth; 
 a driven gear having a plurality of circumferentially spaced teeth that mesh with the teeth of the drive gear whereby rotation of the drive gear results in rotation of the driven gear; 
 a bearing dam that directs a carryover volume from a discharge side of the pump assembly to an inlet side of the pump assembly; 
 a bleed mechanism that supplies bleed fluid flow to the carryover volume disposed between mating drive gear teeth and driven gear teeth, the bleed mechanism including a passage in at least one of the drive gear and driven gear teeth, the passage includes at least one first passage portion extending through the teeth of the drive gear and/or driven gear, the first passage portion having an opening in an axial end of at least one of the drive gear and the driven gear, and the first passage portion extends in a direction substantially parallel to opposite faces of the teeth of the drive and/or driven gear, the passage further communicating with at least one of: 
 (i) a gear face of the drive gear, 
 (ii) a gear face of the driven gear; or 
 (iii) a bottom of a gear tooth profile adjacent a root region between adjacent gear teeth; and 
 the bleed mechanism further comprising an enlarged counter bore portion at an inlet end of the first passage portion that communicates with the inlet side of the gear pump.